Open AccessTHE THERMAL CONTRACTION THEORY OF MOUNTAIN BUILDING
Author(s) -
Hales A. L.
Publication year - 1953
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1953.tb03032.x
Subject(s) - mantle (geology) , geology , contraction (grammar) , crust , seismology , compression (physics) , thermal , geodesy , geophysics , thermodynamics , physics , medicine
Summary The depth of the level of no strain and the stress distribution have been calculated using Jeffreys's temperature distribution. It is found that the depth of the level of no strain is 59 km, that the stress difference in the crust increases at the rate of 0.6 dyn/cm 2 year and that the decrease in the radius in 200 million years is 0.6 km. A relation between the decrease in radius and the heat loss per unit area is derived and from this relation it is shown that the possible changes in the parameters will not bring the contraction into accord with geological estimates. It is pointed out that the stress differences increase much more rapidly in relation to the strength at depths of 250 to 600 km and that failure should begin in this region. On this basis the cross‐sectional area of an ocean deep is found to be 1400 km 2 . The lower mantle and the core are compressed as a result of cooling between the surface and 700 km. This compression is relieved when deep‐focus earthquakes occur. It is calculated that increases in the length of the day totalling about 31/2 sec will occur in a period of failure of the mantle. Using a formula of Lapwood it is shown that the heating effect associated with the compression of the core is of the order of 10 17 erg/sec, and that during failure of the mantle the cooling effect is likely to be much greater. Finally it is shown that the present rate of dissipation of energy in earthquakes is very much greater than the rate of generation of strain energy as a result of cooling.